(1) Field of the Invention
The present invention relates to an electric junction box, which is mounted on a motor vehicle and so on as a mobile unit.
(2) Description of the Related Art
Generally, various electronic equipment such as lamps such as a head lamp and tail lamp, and motors such as a starter motor and motor for an air-conditioner is mounted on a motor vehicle as a mobile unit.
In order to supply electric power to various equipment described above, a junction block has been arranged on a suitable position in a motor vehicle. The junction block is constructed in such a manner that various electric circuit units, such as many fuses and relays, are put together.
In this connection, since the junction block may includes fuses, relays and busbars therein, the junction block is sometimes called a fuse block, relay box or electric junction box as a generic name. In this specification, such a fuse block, relay box or junction block is called an electric junction box as a generic name.
The electric junction box includes a box body forming an outline of the electric junction box, electrical components block mounted in the box body and so on. The box body is formed in a box-shape. The electrical components block includes electrical components such as fuses and relays, which are mounted in the box body, and terminal fittings attached to ends of electric wires.
The terminal fitting is attached to the box body so as to be electrically and mechanically connected to a terminal of an electric component mounted in the box body. The terminal fitting electrically connects an electric wire to an electrical component. An electric wire attached to the terminal fitting is connected to the electronic equipment. The electric junction box constructed as described above electrically connects an electric wire, to which the terminal fitting is attached, to the electrical component such as a relay or fuse according to a predetermined pattern.
The terminal fittings, to which electric wires are attached, as electrical components and electrical components such as relays and fuses are mounted in the box body one by one, thereby the electric junction box is assembled. Therefore, the assembly needs a lot of time and man-hour.
In Japanese Patent Application Laid-Open No. H9-284921, proposed is an electric junction box, in which the box body is provided with a detachable cassette block in which the terminal fittings, relays and fuses are mounted. Such a cassette block is mounted in the box body so that the electrical components such as terminal fittings, relays and fuses are collectively mounted in the box body, thereby reducing time and man-hour for assembly.
The box body of the electric junction box disclosed in Japanese Patent Application Laid-Open No. H9-284921 includes a mounting hole for receiving the cassette block described above. The box body is made of electrically insulating synthetic resin and molded by a known injection molding or the like. The mounting hole is formed being surrounded with a plurality of walls that construct the box body.
Therefore, if the number of the electrical components to be mounted in the cassette block is increased or the size of the electrical component is increased, the rigidity of the box body tends to deteriorate since the box body includes the mounting hole for receiving the cassette block. Therefore, when the cassette block is inserted into the mounting hole, the box body is distorted, causing difficulty in the insertion of the cassette block into the mounting hole.
Moreover, since the box body is made of synthetic resin and molded by a known injection molding or the like, the box body might be distorted when the molded box body is subjected to injection molding or removed from a mold. In such case, of course, the insertion of the cassette block into the mounting hole becomes difficult.